This invention relates generally to wireless communication systems.
Wireless communication has extensive applications in consumer and business markets. Among the many communication applications/systems are: mobile wireless, fixed wireless, unlicensed Federal Communications Commission (FCC) wireless, local area network (LAN), cordless telephony, personal base station, telemetry, encryption, and others. Generally, each of these applications utilizes unique and incompatible modulation techniques and protocols. Consequently, each application may require unique hardware, software, and methodologies for processing digital signals, such as generating the codes required for encoding and for decoding a signal, modulation, demodulation, and other processes. This practice can be costly in terms of design, testing, manufacturing, and infrastructure resources. As a result, a need arises to overcome the limitations associated with the varied hardware, software, and methodologies of processing digital signals in each of the varied applications.
In practice, multiple copies of the same signal are typically received at communications device 100 within a short time of each other. These copies, which are sometimes called multipath components arise because the signals take different paths of different length from the transmitter antenna to the receiver antenna. In the case of a CDMA system, it is feasible and advantageous to despread and decode several of the multipath components, realign them so that they are also in phase and combine them to produce a stronger signal. To do this, the base band processor in a CDMA system typically takes the form of a rake receiver that has several fingers, each one of which is a receiver that despreads and decodes one of the multipath components. General information about rake receivers can be found at pages 972-982 of J. S. Lee, L. E. Miller, CDMA Systems Engineering Handbook (Artech House 1998).
Service providers and network operators often need to support multiple standards with existing rake receivers. Therefore, it is desirable to provide a flexible and programmable generic rake receiver architecture suitable for different spread spectrum systems at a minimal development cost.
A rake receiver in accordance with an exemplary embodiment of this invention provides an integration of generic, inexpensive components in a fully configurable manner. The rake receiver is configurable by an external agent (e.g., microcontroller, DSP, or state machine) to suit the particular requirements of each system. In an exemplary embodiment, each finger in the rake receiver includes multiple generic despreaders/descramblers, multiple generic dechannelizers coupled to the despreaders/descramblers, and at least one timing estimation controller coupled to the despreaders/descramblers. Each finger also includes at least one phase estimation controller, at least one frequency estimation controller, and at least one energy estimation controller all coupled to the dechannelizers.